Goals of Treating Breast Cancer (Mammary Gland Tumors)

The primary goal of treating a dog with breast cancer is to surgically and completely remove all cancerous masses along its mammary chain. If the tumors are inoperable or have already spread, or if the owner is unable or unwilling to proceed with the surgery either financially or otherwise, the therapeutic goal becomes to manage the disease so as to improve or at least maintain the dog’s quality of life for as long as possible.

Treatment Options for Breast Cancer (Mammary Gland Tumors)

The best treatment option for dogs with breast cancer is to have all mammary tumors, whether benign or malignant, removed with wide surgical margins (this means that there will be at least 2 centimeters of clean, healthy tissue around all sides of the tumor after it is removed). Several surgical techniques are available, depending on the size, location and number of tumors: 1) removing just a mass with a rim of healthy tissue (lumpectomy/nodulectomy); 2) removing the entire affected mammary gland (simple or regional mastectomy); or 3) removing all mammary glands on one or both sides of the body (unilateral or bilateral radical mastectomy). These all can all be performed in our companion dogs.

Chemotherapy is offered at many veterinary teaching hospitals and specialized referral hospitals with oncology expertise. Chemotherapy involves administering highly toxic drugs slowly but directly into a dog’s veins. The drugs target and kill rapidly-dividing cells, which include malignant cancer cells. Unfortunately, hair cells, cells lining the stomach and intestinal tract and other important cell types also divide rapidly. Chemotherapy has potentially devastating side effects; owners should consult with an experienced veterinary oncologist to learn about the latest treatment options and all of their potential side effects. Radiation therapy is also available at limited locations. Many dogs with cancer benefit from pain medication, especially late in the course of their disease.

Prognosis and Outlook

The outlook for dogs with breast cancer depends on whether their tumors are malignant or benign. Dogs with benign tumors that are surgically removed with clean wide margins have an excellent prognosis and often are considered to be “cured.” The outlook for dogs with malignant masses varies tremendously based on tumor type, tumor size, lymph node involvement and the extent of metastasis. The prognosis can range from good to guarded to grave.

Special Notes

The jury is still out on whether chemotherapy will delay or reduce the risk of a solitary malignant mammary gland tumor metastasizing to other areas. Owners who detect any lump or bump on or around the mammary glands of their dog should consult a veterinarian immediately. Swift diagnosis and treatment can be life-saving, even if the tumor is “one of the bad ones.”